Expandable guide sheath and apparatus and methods for using such sheaths

ABSTRACT

Apparatus and methods are provided for accessing body lumens and/or for delivering instruments into body lumens, e.g., vessels within a patient&#39;s vasculature. A flexible sheath is provided that is expandable from a contracted condition to an enlarged condition wherein the sheath at least partially defines a lumen therein. The sheath is lubricious and has a relatively thin wall, thereby providing a collapsible/expandable guide for delivering fluids and/or instruments through tortuous anatomy and/or into relatively narrow passages. The sheath is advanced from an entry site to a body lumen in the contracted condition. Once the sheath reaches a target body lumen, the sheath is expanded to the enlarged condition, thereby defining a lumen within the sheath, and fluids and/or instruments are introduced into the body lumen via the sheath lumen. Upon completing the procedure, the sheath is removed from the body lumen.

This application is a continuation of co-pending application Ser. No.10/423,321, filed Apr. 24, 2003, now U.S. Pat. No. 7,762,995, whichclaims benefit of provisional application Ser. No. 60/376,065, filedApr. 25, 2002, the disclosure of which is expressly incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods fordelivering instruments and/or agents during a medical procedure, and,more particularly, to guide sheaths for accessing body lumens and/ordelivering instruments into body lumens of a patient.

BACKGROUND

Minimally invasive procedures have been implemented in a variety ofmedical settings, e.g., for vascular interventions, such as angioplasty,stenting, embolic protection, electrical heart stimulation, heartmapping and visualization, and the like. These procedures generally relyon accurately navigating and placing instruments within a patient'svasculature.

During such procedures, a target vessel may be accessed using aguidewire advanced through the intervening vasculature into the targetvessel, thereby providing a “railway” to the vessel. One or moreinstruments, e.g., catheters, sheaths, and the like, may be advancedover the guidewire or “rail” into the vessel. Thus, a diagnostic and/ortherapeutic procedure may be performed by advancing one or moreinstruments over this railway.

There are many risks involved with advancing instruments over aguidewire. For example, a catheter or other instrument may skive orotherwise damage a wall of a vessel, particularly as the instrumentpasses through narrow passages or tortuous anatomy involving sharpbends. Such instruments also risk dislodging embolic material or evenperforating the vessel wall.

In addition, it is often desirable to access very small vessels deepwithin the body, e.g., within a patient's heart, for example, to place aventricular pacing lead within a coronary vein. However, theinstrument(s), e.g., guide sheath, lead, etc., may have a relativelylarge cross-section and/or may have a relatively blunt distal tip,making it difficult to advance such instruments as deeply as desiredinto such small vessels.

Accordingly, apparatus and methods for delivering instruments into bloodvessels or other body lumens and/or for otherwise accessing vessels orother body lumens would be useful.

SUMMARY OF THE INVENTION

The present invention is directed generally to apparatus and methods forproviding access to body lumens and/or for delivering instruments and/oragents into body lumens during a medical procedure. More particularly,the present invention is directed to guide sheaths and methods for usingsuch sheaths to facilitate delivering instruments and/or agents intobody lumens of a patient, e.g., within the patient's coronary, neuro,and/or peripheral vasculature, within the patient's gastrointestinaltract, urogenital tract, respiratory tract, lymphatic system, and/orwithin surgically created passages.

In accordance with one aspect of the present invention, a sheathapparatus is provided that includes an elongate expandable sheath thatmay be expandable from a contracted condition to minimize a profile ofthe sheath, e.g., to allow insertion into a body lumen, to an enlargedcondition wherein the sheath at least partially defines a lumen therein.The sheath may be formed from a lubricious material, a polymer, and/oran elastomeric material, preferably having a relatively thin wall,thereby providing a tubular sheath that may be substantially flexibleand/or flimsy. For example, the sheath may include a wall thicknessbetween about 0.001-1.25 millimeter, and preferably between about0.005-0.06 millimeter.

Optionally, the sheath may include one or more reinforcing elementsextending along the sheath, e.g., axially, helically, and/orcircumferentially around the sheath. Such reinforcing elements maysupport the sheath during delivery and/or may enhance the sheathassuming a desired shape and/or size in the enlarged condition. Inaddition or alternatively, a stiffening or reinforcing member may beprovided for supporting or otherwise carrying the sheath to facilitateits introduction in the contracted condition. Optionally, the sheathand/or stiffening member(s) may be coated, e.g., with an anti-thromboticagent and/or hydrophilic coating.

Preferably, the expandable sheath includes a proximal end, a distal end,and has a length sufficient to extend between an entry site into apatient's body and a target body lumen, e.g., between about two andthree hundred centimeters (2-300 cm), and preferably between abouttwenty and one hundred fifty centimeters (20-150 cm). In one embodiment,the sheath may be a tubular member, while, in another embodiment, thesheath may include a sheet of material whose edges are attached to astiffening member such that the sheet and the stiffening member togetherdefine the lumen.

The distal end of the sheath may include an opening communicating withthe lumen such that an instrument inserted through the lumen may beadvanced from the opening into a body lumen. Alternatively, the distalend of the sheath may be substantially closed and/or may include abreak-away portion for creating an opening such that an instrumentinserted through the lumen may be advanced from the opening into a bodylumen. Optionally, the sheath may include a fixation device, e.g., anexpandable cuff or balloon, on the distal end for substantially securingthe apparatus at a location within a body lumen, e.g., to preventmovement during delivery of a treatment device through the sheath.

In accordance with another aspect of the present invention, an apparatusis provided that includes a flexible stiffening member having proximaland distal ends, and an expandable sheath. The sheath may extend betweenthe proximal and distal ends of the stiffening member, and may beexpandable from a contracted condition to minimize a profile of thesheath, and an enlarged condition wherein the sheath at least partiallydefines a lumen extending at least partially between the proximal anddistal ends of the stiffening member. Similar to the previousembodiments, the sheath may be formed from a lubricious material, apolymer, and/or an elastomeric material, preferably having a relativelythin, flexible and/or flimsy wall.

The stiffening member may include one or more strands extending alongthe sheath, e.g., extending axially, helically, and/or circumferentiallyaround the sheath. In a preferred embodiment, the stiffening member isan elongate member for carrying the sheath and having sufficient columnstrength that the distal end of the stiffening member may be advancedthrough a body lumen by pushing the proximal end of the stiffeningmember without substantial risk of kinking or buckling. For example, thestiffening member may be a guidewire, a catheter, or other cylindricalmember about which the sheath may be wrapped or otherwise maintained inthe contracted condition. Alternatively, the stiffening member mayinclude an arcuate cross-section, thereby defining a groove extendingbetween the proximal and distal ends within which the sheath may be atleast partially disposed in the contracted condition.

The sheath may be attached to the stiffening member at one or morelocations, e.g., at the distal end of the stiffening member, at both theproximal and distal ends of the stiffening member, at intermediatelocations between the proximal and distal ends, and/or continuouslyalong the stiffening member. In addition or alternatively, the sheathmay be detachably secured to the stiffening member. Optionally, aconstraint may be provided for selectively maintaining the sheath in thecontracted condition. For example, the stiffening member and sheath maybe disposed within a catheter or other tubular member, and/or one ormore filaments may be disposed around the sheath to maintain the sheathin the contracted condition.

In accordance with yet another aspect of the present invention, a methodis provided for accessing a body lumen of a patient. The body lumen maybe, for example, a vessel or other passage within a patient's urogenitaltract, respiratory tract, gastrointestinal tract, lymphatic system, orvascular system. In addition or alternatively, the body lumen may be apassage surgically created within the patient, e.g., an interstitialspace accessed via a surgically-created entry site.

Generally, an expandable sheath is advanced from an entry site to a bodylumen with the sheath in a contracted condition. The sheath may beadvanced over a guide wire or in conjunction with another rail.Preferably, the sheath is advanced from the entry site until a distalend of the sheath is disposed within the body lumen while a proximal endof the sheath remains outside the entry site.

Once the sheath reaches the target body lumen, the sheath may beexpanded to an enlarged condition, thereby defining a lumen within thesheath, e.g., that extends from the entry site to the target body lumen.The sheath may be expanded to the enlarged condition, e.g., byintroducing a fluid into the lumen defined by the sheath, such assaline, contrast, carbon dioxide, oxygen, and/or air, and/or byintroducing an instrument into the lumen defined by the sheath.

A diagnostic and/or therapeutic procedure may be performed within thebody lumen via the lumen defined by the sheath. In one embodiment, theentry site may be a percutaneous site communicating with the patient'svasculature, and the body lumen may be a blood vessel, e.g., within thepatient's coronary, peripheral, or neuro vasculature. The procedure mayinclude introducing one or more instruments or agents through the lumendefined by the sheath into the target blood vessel, e.g., a catheter, aguidewire, a balloon, a stent, a filter, a pacing lead, an atherectomydevice, a thrombectomy device, and/or a medicament (e.g.,anti-inflammatory drug, anti-thrombotic agent, inhibitors, and thelike). In a preferred embodiment, the target blood vessel may be astenotic or occluded region within an artery. In another preferredembodiment, the target blood vessel may be a coronary vein, and the oneor more instruments may include an electrical lead.

Upon completing the procedure, the sheath may be removed from the bodylumen. Optionally, the sheath may be at least partially collapsed fromthe enlarged condition before removing the sheath from the body lumen,e.g., by creating a vacuum within the sheath and/or by withdrawing thesheath into a catheter or other tubular member. Alternatively, thesheath may be split along a single longitudinal seam, or along two ormore seams into two or more pieces to facilitate removal from the bodylumen.

Thus, a sheath in accordance with the present invention may provide aprimary access device that is substantially flexible, collapsible,and/or compliant. This primary device may assume a relatively lowprofile to facilitate advancement through narrow passages and/ortortuous anatomy, e.g., into difficult to access locations deep within apatient's body. Once a desired location is reached, the primary devicemay be released and/or expanded, and one or more secondary device(s) maybe advanced through the primary device. The primary device may provide alubricious path, prevent dissection of a vessel wall, and/or otherwisefacilitate delivering the secondary device(s) into difficult to accesslocations. The primary device may be free to expand to accommodate thesecondary device(s) and/or to substantially translate axial forces,e.g., caused by pushing the secondary device(s), into radial forces,thereby minimizing risk of damage to the passages through which thesecondary device(s) is(are) advanced.

In accordance with another aspect of the present invention, an apparatusis provided for delivering an instrument, e.g., a guidewire, into a bodylumen of a patient, e.g., across a total occlusion within a bloodvessel. The apparatus generally includes a catheter or other elongateand/or tubular member including proximal and distal ends, and anexpandable sheath attached to an outer surface of the catheter. Thesheath, e.g., a flexible and/or flimsy tubular member and/or sheet, maybe expandable from a contracted condition to minimize a profile of thesheath, and an enlarged condition wherein the sheath at least partiallydefines an accessory lumen extending between proximal and distal ends ofthe sheath.

In accordance with yet another aspect of the present invention, a methodis provided for delivering an instrument through an occlusion in a bodylumen using a catheter or other elongate member including an expandablesheath extending along an outer surface of the elongate member. A distalend of the catheter may be introduced into the body lumen proximal tothe occlusion with the sheath in a contracted condition. The distal endof the catheter may be advanced through the occlusion until a distal endof the sheath is disposed distal to the occlusion. The distal end of thecatheter may include one or more elements for facilitating advancing thedistal end through the occlusion, e.g., an imaging element, a dissectionelement, and/or a steering element.

An instrument, e.g., a guidewire or other elongate member, may beadvanced through the sheath until a distal end of the instrument isdisposed distal to the occlusion. The sheath may be expanded beforeinserting the instrument, e.g., by introducing fluid into the lumen ofthe sheath, or the sheath may be expanded as the instrument is insertedinto the sheath.

The catheter and sheath may then be withdrawn from the body lumen, e.g.,leaving the guidewire or other elongate member across the occlusion. Oneor more instruments may be advanced over the guidewire, e.g., after thecatheter is withdrawn to observe and/or treat the occlusion.

Other objects and features of the present invention will become apparentfrom consideration of the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are partial cross-sectional side views of a firstpreferred embodiment of a sheath apparatus, including an expandablesheath and a stiffening member, showing the sheath in contracted andexpanded conditions, respectively.

FIGS. 2A and 2B are cross-sections of the apparatus of FIGS. 1A and 1Btaken along lines 2A and 2B, respectively.

FIGS. 3A-3C are alternate cross-sections of a stiffening member that maybe incorporated into a sheath apparatus.

FIGS. 4A and 4B are cross-sectional views of an alternative embodimentof a sheath apparatus, including an expandable sheath attached to astiffening member, such as that shown in FIG. 3A, showing the sheath incontracted and expanded conditions, respectively.

FIG. 5 is a perspective detail of a distal end of a sheath apparatus,including an expandable sheath having a weakened region for creating anopening in a wall thereof

FIG. 6 is a perspective detail of an alternative distal end of a sheathapparatus, including an expandable sheath including a beveled distal endhaving an opening therein.

FIG. 7 is a side view of an alternative embodiment of a sheathapparatus, including an expandable sheath with an inflatable cuff on oneend.

FIG. 8 is a partial cross-sectional side view of a sheath apparatusincluding wire loops wrapped around an expandable sheath to constrainthe sheath in a contracted condition.

FIGS. 9A and 9B are perspective details of a sheath apparatus, showingan expandable sheath in contracted and expanded conditions,respectively.

FIGS. 10A and 10B are perspective details of another embodiment of asheath apparatus, showing an expandable sheath in contracted andexpanded conditions, respectively.

FIGS. 11A-11F are partial cross-sections of a patient's vasculature,showing a method for delivering a stent across a stenosis using a sheathapparatus, in accordance with the present invention.

FIGS. 12A-12D are partial cross-sections of a patient's heart, showing amethod for delivering an electrical lead into a coronary vein using asheath apparatus, in accordance with the present invention.

FIGS. 13A and 13B are side views of another embodiment of a sheathapparatus including a tubular constraint from which the apparatus may bedeployed.

FIGS. 14A-14C are partial cross-sectional views of a patient's colon,showing a method for delivering a colonoscope using a sheath apparatus,in accordance with the present invention.

FIGS. 15A-15D are partial cross-sectional views of a vein, showing amethod for delivering a stent through valves of the vein.

FIGS. 16A-16C are perspective details of another embodiment of a sheathapparatus including an outer sheath that may separate to accommodateexpansion of an expandable sheath therein.

FIGS. 17A-17C are cross-sectional views of the apparatus shown in FIGS.16A-16C, respectively.

FIG. 18 is a side view of another embodiment of an apparatus including acatheter and an expandable sheath, in accordance with the presentinvention.

FIGS. 19A-19C are cross-sections of the apparatus of FIG. 18, showingthe sheath contracted, expanded, and with a guidewire therein,respectively.

FIGS. 20A-20D are cross-sectional views of a blood vessel, showing amethod for delivering a guidewire across an occlusion in the vessel.

FIGS. 21A and 21B are cross-sections of alternate embodiments of theapparatus of FIGS. 1A and 1B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to the drawings, FIGS. 1A-2B show a first preferred embodimentof an apparatus 10 for providing access within a body lumen (not shown)and/or for delivering one or more instruments (also not shown) within abody lumen, such as a vessel within a patient's vasculature, a passagewithin a patient's gastrointestinal tract, urogenital tract, respiratorytract, lymphatic system, and the like.

Generally, the apparatus 10 includes a flexible elongate stiffeningmember 12 providing a “backbone” for the apparatus 10, and an expandablemembrane or sheath 20. The stiffening member 12 includes a proximal end14 and a distal end 16 defining a longitudinal axis 18 therebetween. Inaddition, the stiffening member 12 may have sufficient length to beadvanced from a location outside a patient's body (not shown) throughany intervening body passages into a site to be accessed and/or treated.The distal end 16 may have a size and/or shape for insertion into a bodylumen, e.g., including a rounded or other substantially atraumaticdistal tip 17, a “J” tip (not shown), and the like.

In one embodiment, the stiffening member 12 may be a solid or hollowguidewire, a catheter, a thread, and the like. Preferably, thestiffening member 12 is substantially flexible to facilitate advancementthrough tortuous anatomy without causing dissection or perforation, yethas sufficient column strength and/or torque-ability that the distal end16 may be advanced through a body lumen by pushing the proximal end 14without substantial risk of kinking and/or buckling. The stiffeningmember 12 may include one or more lumens 19 (shown in FIGS. 2A and 2B)extending between the proximal and distal ends 14, 16, e.g., to allowfluids to be delivered therethrough and/or to receive a guide wire orother instrument (not shown) therethrough.

The stiffening member 12 may have a substantially symmetricalcross-section, e.g., a cylindrical cross-section, as shown in FIGS. 2Aand 2B, or may have an asymmetrical cross-section, e.g., an arcuatecross-section, as shown in FIGS. 3A-4B. In the embodiments shown inFIGS. 3A-4B, the stiffening member 112 may define a groove 113 extendingat least partially between its proximal and distal ends (not shown inFIGS. 3A-4B).

The stiffening member 12 or 112 may be formed from a variety ofmaterials and using various methods known in the art. For example, thestiffening member may be formed from plastic, glass, composite, and/ormetal using known methods, such as extrusion and the like, therebyproviding a desired combination of flexibility and column strength. Asused herein, the terms “backbone,” “backbone member,” or “stiffeningmember” may include any elongate flexible structure capable ofsupporting or reinforcing an expandable membrane or other sheath tofacilitate introducing the sheath into a body lumen of a patient and/orto facilitate tracking a secondary device along the axis of the sheathand/or over the entire apparatus. The stiffening member 12 may have adiameter or other maximum cross-section between about 0.05-5millimeters, and preferably between about 0.2-2 millimeters.

Returning to FIGS. 1A and 1B, the expandable membrane or sheath 20includes a proximal end 22, a distal end 24, and one or more side wallsextending between the proximal and distal ends 22, 24, thereby at leastpartially defining a lumen 26. As used herein, the term “sheath” or“guide sheath” may include any structure that at least partially definesa lumen, whether the structure is substantially tubular or onlypartially defines the lumen.

The sheath 20 may be expandable from a contracted condition, as shown inFIGS. 1A and 2A, to an enlarged condition, as shown in FIGS. 1B and 2B.When the sheath 20 is in a contracted condition, the apparatus 10 mayassume a low profile to facilitate insertion into a body lumen (notshown). For example, as best seen in FIG. 2A, the sheath 20 may befolded, twisted, wrapped, or otherwise compressed around or adjacent tothe stiffening member 12 (e.g., using an internal vacuum with the lumen26 of the sheath 20 and/or an external force). In the enlargedcondition, the sheath 20 may unfold, untwist, unwrap, or otherwiseexpand to at least partially define the lumen 26, e.g., for receiving afluid (e.g., a medicament, anti-thrombotic agent, and the like) and/orone or more instruments therethrough (not shown).

Because the sheath 20 is relatively thin-walled, the apparatus 10 mayattain a relatively low profile when the sheath 20 is in its contractedcondition, e.g., between about 0.1 and about ten millimeters (0.1-10mm), and preferably between about 0.2 and about three millimeters (0.2-3mm). Conversely, a relatively large lumen 26 may be provided when thesheath 20 is expanded to the enlarged condition, e.g., having a diameteror other maximum cross-section between about 0.3 and about one hundredmillimeters (0.3-100 mm), and preferably between about 0.3 and abouttwenty millimeters (0.3-20 mm).

The sheath 20 may be formed from relatively thin, flexible material, ascompared to the stiffening member 12. Thus, the sheath 20 may be flimsy,i.e., may have little or no rigidity such that the sheath 20 provideslittle resistance to expansion and/or contraction, and/or may conformsubstantially to anatomy within which it is deployed. As used herein,“flimsy” means that the material of the sheath 20 is not biased toassume any particular configuration or shape, and therefore, the sheath20 may adopt whatever shape and/or configuration that is imposed uponit, e.g., by being folded or otherwise compressed, by being subjected tointernal pressure or force, and the like. To achieve this, the sheath 20may have a relatively thin wall thickness, e.g., between about0.001-1.25 millimeters, and preferably between about 0.005-0.06millimeter.

The sheath 20 may be constructed of materials that may be fabricated toa relatively thin, flexible configuration, e.g., polytetrafluoroethylene(PTFE), expanded polytetrafluoroethylene (EPTFE), fluorinated ethylenepropylene (FEP), polyethylene teraphathalate (PET), urethane, olefins,polyethylene (PE), silicone, latex, isoprene, chronoprene; and the like.The sheath 20 may be formed from a lubricious material and/orhydrophilically coated with a liquid silicone or other coating, e.g.,for facilitating inserting one or more instruments (not shown) throughthe lumen 26. Preferably, the sheath 20 is formed from substantiallyinelastic material, i.e., such that a primary contribution to the sheath20 expanding and contracting is unfolding or folding the material of thesheath 20. Thus, a total peripheral length of the sheath 20 may notchange substantially between the contracted and enlarged conditions.Alternatively, the sheath 20 may be formed from an elastic material suchthat a secondary contribution to the sheath 20 expanding and contractingis an elasticity of the material of the sheath 20, i.e., such that theperipheral length of the sheath 20 may increase as the sheath 20 expandstowards the enlarged condition.

The sheath 20 may be substantially nonporous. Alternatively, the sheath20 may be porous, for example, substantially continuously along itslength or at one or more locations, e.g., to allow fluid delivered intothe lumen 26 to pass through the wall of the sheath 20 in a desiredmanner, e.g., to deliver fluid to a wall of a vessel (not shown) throughwhich the sheath 20 extends. In a further alternative, the sheath 20 mayinclude one or more discrete openings (not shown) at one or morelocations along its length.

In addition or alternatively, the sheath 20 may include a thin-walledmetal foil. Alternatively, the sheath 20 may include a thin mesh, e.g. aperforated urethane film and the like. In a further alternative, thelubricity of the sheath 20 may be enhanced by providing a lubriciouscoating, lining, ribbing, and the like (not shown), and/or applying alubricant, e.g., to the interior surface of the sheath 20. The sheath 20may include a single layer or multiple layers of such materials, suchthat a desired flexibility and lubricity is achieved. Thus, the sheath20 may easily expand and/or line a body lumen to reduce friction and/oraccommodate instruments being advanced through the body lumen, asexplained further below.

Optionally, the sheath 20 may include one or more reinforcing elements(not shown). For example, a wire, thread, filament, and the like, formedfrom plastic, glass, composite, and/or metal, may be attached to anouter surface, an inner surface, and/or embedded in a wall of the sheath20. In addition or alternatively, the sheath 20 may include relativelythickened regions that may be formed directly from the wall material.The reinforcing element(s) may extend circumferentially and/or helicallyaround the sheath 20, and/or may extend axially along the sheath 20,depending upon the reinforcement desired. The reinforcement element(s)may also bias the sheath 20 assume a desired shape or configuration whenexpanded towards the enlarged condition.

In alternative embodiments, the sheath may be a tubular structure or apartially tubular structure of braided material (not shown) that may beattached to a stiffening member to provide a sheath apparatus. Forexample, the sheath may be formed from one or more plastic and/or metalwires, threads, or other strands that are braided, woven, and/or knitinto a tubular body or into a sheet whose edges may be attached to astiffening member, similar to the embodiments described elsewhereherein. The braided strands may be compressed to the contractedcondition by twisting, folding, crimping, and/or wrapping, as describedabove, and/or by axial translation, e.g., pulling opposite ends of thesheath away from one another to cause the braided strand(s) to compressradially under the axial tension.

The proximal end 22 of the sheath 20 may include an annular collar orhandle that may facilitate manipulating the sheath 20 and/or insertingone or more instruments into the lumen 26. In addition or alternatively,the proximal end 22 may include a hemostatic valve (also not shown) thatmay substantially seal the lumen 26 from proximal flow of fluid, yet mayallow instruments to be introduced into the lumen 26, as is known in theart. For example, as shown in FIGS. 1A and 1B, a toughy borst valve 23may be provided on the proximal end 22 of the sheath 20, e.g., tocontrol passage into the lumen 26. Alternatively, other structures maybe provided, e.g., a slit valve adapter, a removable clamp, an o-ring, aside port, an adjustable fixation device, and the like (not shown), forselectively sealing the lumen 26, manipulating the sheath 20, and/or forfacilitating introducing instruments into the sheath 20.

The distal end 24 of the sheath 20 may include a variety ofconfigurations. For example, as shown in FIGS. 1A and 2A, the distal end24 of the sheath 20 may be offset proximally from the distal tip 17 ofthe stiffening member 12. In addition, the distal end 24 may include arounded shape (e.g., as shown in FIG. 2A), a beveled shape (e.g., asshown in FIG. 6), or other tapered shapes that may enhance atraumaticadvancement of the apparatus 10.

For example, as shown in FIG. 6, the taper 28″ of the distal end 24″ ofthe sheath 20″ may facilitate tracking the apparatus 10″ over a guidewire (not shown) and/or may facilitate advancing the apparatus 10″through a body lumen (also not shown). The taper 28″ may minimize riskof the sheath 20″ catching and/or may cause the sheath 20″ to collapsetowards the contracted condition as the apparatus 10″ is advancedthrough a body lumen without needing external constraint. Alternatively,the distal end of the sheath may be substantially blunt (not shown).

The distal end 24 of the sheath 20 may be substantially closed or mayinclude one or more openings. For example, as shown in FIG. 2A, thedistal end 24 of the sheath 20 may be attached to the distal end 16 ofthe stiffening member 12 to substantially close the lumen 26 at thedistal end 24. The distal end 24 of the sheath 20 may be detachable fromthe stiffening member 12 to release the sheath 20 from the stiffeningmember 12.

For example, the distal end 24 of the sheath 20 may be attached to thestiffening member 12 by an adhesive, solder, or other bonding materials,yet may be torn free or otherwise separated from the distal end 16 ofthe stiffening member 12, e.g., by pulling the sheath 20 proximallyrelative to the stiffening member 12 or by pushing the stiffening member12 distally relative to the sheath 20. Alternatively, an instrument (notshown) may be advanced through the expandable member 20 and pushedagainst the closed distal end 24 to cause the distal end 24 to separatefrom the stiffening member 12. This may create an opening (not shown) inthe distal end 24 of the sheath 20 through which fluid and/or one ormore instruments (also not shown) may be advanced.

Alternatively, a mechanical connector (not shown) may be provided thatmay secure the distal ends 16, 24 together, and that may be actuated torelease the distal end 24 of the sheath 20 from the distal end 16 of thestiffening member 12. In further alternatives, a cinch loop (not shown)may be provided on the distal end 24 that may be selectively opened orclosed, or a removable clip (also not shown) may be provided. Inaddition or alternatively, the distal end 24 of the sheath 20 may bebonded to the distal end 16 of the stiffening member 12, e.g., using abioabsorbable adhesive or other material that may dissolve when exposedto bodily fluids to provide an opening (not shown).

In a further alternative, shown in FIG. 5, the distal end 24′ of thesheath 20′ may include a break-away or penetrable region, e.g., arelatively thin or otherwise weakened region 30′ of the sidewall of thesheath 20.′ The weakened region 30′ may tear along a weakened seam ormay be punctured (not shown) when an instrument (also not shown) withinthe lumen 26′ is pushed against the weakened region 30′ to create anopening, thereby allowing the instrument to be advanced through theopening into the body lumen.

In yet another alternative, shown in FIG. 6, the distal end 24″ of thesheath 20″ may include one or more openings 28″ communicating with thelumen 26,″ e.g., an axial opening defined by the tapered distal end 24,″such that an instrument (not shown) inserted through the lumen 26″ maybe advanced from the opening 28″ and into the body lumen.

Alternatively, as shown in FIG. 7, the distal end 424 of the sheath 420may include an expandable cuff 430. The cuff 430 may be an inflatableannular balloon attached around a periphery of the sheath 420. One ormore lumens (not shown) may be provided within the stiffening member 412that communicate with the interior of the cuff 430 to expand and/orcollapse the cuff 430. The expanded cuff 430 may be used to fix thesheath 420 within a body lumen (not shown) and/or may serve to isolate adistal segment of a body lumen from a segment proximal to the expandedcuff 430.

For example, the sheath 420 may be delivered into a blood vessel, andthe cuff 430 may be expanded to seal the vessel. One or moreintravascular manipulations or procedures may be performed within thevessel proximal to the expanded cuff 430. Thus, if embolic debris isreleased within the proximal portion of the vessel, the cuff 430 mayprevent the debris from passing to the distal portion of the bloodvessel.

In another alternative, the proximal opening 426 of the sheath 420 maybe positioned within a blood vessel (not shown), thereby creating abypass or shunt channel that may be positioned within a body lumenbeginning at the proximal opening 426 and extending through the lumen426 of the sheath 420 to the distal cuff 430. In a further alternative,one or more lumens (not shown) may be created within or along a wall ofthe sheath 420 itself Optionally, one or more cuffs or pockets (notshown) may be provided at one or more locations along the sheath 420,e.g., to anchor the sheath 420, to restrict flow, e.g., for the purposeof retrograde infusion of contrast, and/or to bias the sheath 420 toexpand to a particular shape or configuration.

Returning to FIGS. 1A-2B, in one embodiment, the sheath 20 may be asubstantially enclosed tubular body that is attached to the stiffeningmember 12 at one or more locations between the proximal and distal endsof the stiffening member 12. For example, the sheath 20 may be attachedto the stiffening member 12 only at the distal ends 24, 16.Alternatively, the sheath 20 may be attached to the stiffening member 12at or near the proximal end 22, the distal end 24 of the sheath 20, orboth, e.g., when the stiffening member 12 is disposed along a wall ofthe sheath 20.

Optionally, the sheath 20 may be attached to the stiffening member 12intermittently, e.g., at one or more additional locations between theproximal and distal ends 22, 24. Alternatively, the stiffening member 12may be attached substantially continuously to the sheath 20 between theproximal and distal ends 22, 24 of the sheath 20. The stiffening member12 may be attached to an interior of the sheath 20, i.e., within thelumen 26, or, alternatively, may be attached to an exterior of thesheath 20. The sheath 20 and the stiffening member 12 may be attached toone another using any known method, e.g., bonding with adhesive, sonicwelding, sutures or other strands (not shown) and the like.

Alternatively, as shown in FIGS. 21A and 21B, the stiffening member 12may be received in a separate pocket or lumen 27 of the sheath 20 thatextends between the proximal and distal ends 22, 24 of the sheath 20.The stiffening member 12 may be loose within the pocket or lumen 27(FIG. 21) or may be attached to the sheath 20 within the lumen 27 (FIG.21B), as described above.

In another embodiment, shown in FIGS. 4A and 4B, the sheath 120 may be asheet of material whose edges 121 are attached to a stiffening member112. Thus, the stiffening member 112 may partially define the lumen 126,along with the sheet of the sheath 120. The sheath 120 may be attachedsubstantially continuously along the length of the stiffening member112, although, alternatively, the sheath 120 may be attachedintermittently to the stiffening member 112, as described previously.

Optionally, any of the sheaths described above, e.g., the sheath 20shown in FIGS. 1A-2B may be configured to split, e.g., along one or moreseams (not shown) extending at least partially from the proximal end 22towards the distal end 24, and/or to separate from the stiffening member12. For example, the sheath 20 may include two or more sets ofintermittent perforations and/or relatively thin-walled seams (notshown) that extend between the proximal and distal ends 22, 24. Inaddition or alternatively, the material of the sheath 20 may be biasedto tear preferentially, e.g., along the longitudinal axis 18, toseparate the sheath 20 into two or more longitudinal strips (not shown).These features may facilitate removing the sheath 20 and/or the entireapparatus 10 from a body lumen when an instrument (not shown) isdisposed within the lumen 26, for example, when the instrument isintended to be substantially permanently implanted within the bodylumen.

The apparatus 10 may also include a constraint for covering and/orprotecting the sheath during advancement through a patient's vasculatureor other body passages. For example, as shown in FIG. 8, one or morewires, threads, monofilaments, or other strands 50 may be disposedaround the sheath 20 to maintain the sheath 20 in its contractedcondition. The strands 50 may include a plurality of loops 52 thatextend around the sheath 20 and are secured using one or more removablefilaments (not shown) fed through the loops 52. To release the sheath20, the removable filament(s) may be removed from the loops 52, e.g., bypulling the removable filament(s) from the proximal end of the apparatus10. The loops 52 may then be released and their strand(s) may beremoved.

Alternatively, other constraints, e.g., wraps, ties, adhesives,bio-absorbable encapsulating materials, e.g., sucrose, and the like, maybe used (not shown). In further alternatives, a catheter, sheath, orother tubular member (also not shown) may be provided. For example, asshown in FIGS. 13A and 13B, a catheter 80 may be used that may include alumen 82 within which the apparatus 10 (or any other sheath apparatusdescribed herein) may be disposed when the sheath 20 is in thecontracted condition. The apparatus 10 may include a pushing element 84,e.g., a wire or other elongate member extending from the stiffeningmember 12 (see FIGS. 1A-2B, not shown in FIGS. 13A and 13B). The pushingelement 84 may be advanced distally relative to the catheter 80 todeploy the apparatus 10, as shown in FIG. 13B, or may be pulledproximally to retract the apparatus 10 into the catheter 80, as shown inFIG. 13A.

In another embodiment, shown in FIGS. 16A-17C, an outer sheath 180 maybeprovided that is at least partially bonded to a sheath apparatus 110 tomaintain an expandable sheath 120 in a contracted condition. The outersheath 180 may be formed from materials similar to the expandable sheath120, e.g., having a wall thickness between about 0.005-0.06 millimeter(mm). Thus, the outer sheath 180 may be substantially flexible and/orconformable to facilitate advancing the apparatus 110 and outer sheath180 through a body lumen of a patient.

The apparatus 110 may include a stiffening member 112, similar to thatdescribed above with reference to FIGS. 3A-4B, to which the expandablesheath 120 may also be attached, similar to other embodiments describedabove. The stiffening member 112 may include one or more lumens 119(three exemplary lumens being shown), and the outer sheath 180 may bebonded or otherwise attached to the stiffening member 112, e.g.,continuously or intermittently along a length of the stiffening member112. The lumen(s) in the stiffening member 112 may provide infusion,aspiration, agitation, and/or perfusion through the apparatus 110, e.g.,from the proximal end to the distal end of the apparatus 110.Alternatively, the outer sheath 180 may be attached directly to theexpandable sheath 120, e.g., at a location around the periphery and/oralong a length of the expandable sheath 120 (not shown).

As best seen in FIGS. 16A and 17A, the outer sheath 180 may at leastpartially define a lumen 182 (either alone or along with the stiffeningmember 112) within which the expandable sheath 120 may be received inits contracted condition. In addition, the outer sheath 180 may includeone or more weakened regions 186, e.g., extending between proximal anddistal ends (not shown) of the outer sheath 180. The weakened region(s)186 may include intermittent perforations and/or continuous orintermittent thin-walled regions that may extend, e.g., substantiallyaxially along the outer sheath 180.

The weakened region(s) 186 may separate upon exposure to internalpressure to allow the expandable sheath 120 to expand towards itsenlarged condition. For example, fluid may be introduced into the lumen182 of the outer sheath 180 until sufficient pressure develops to causethe weakened region(s) 186 to tear or otherwise separate. Alternatively,fluid or an instrument (not shown) may be introduced into the expandablesheath 120 such that the expandable sheath 120 expands until it pushesradially outwardly against the outer sheath 180 and causes the weakenedregion(s) 186 to separate.

For example, during use, the apparatus 110 and outer sheath 180 may beadvanced through a body lumen, e.g., a blood vessel and the like (notshown), with the outer sheath 180 intact and the expandable sheath 120in its contracted condition, as shown in FIGS. 16A and 17A. Once adesired location is reached, internal pressure may be applied toseparate the weakened region(s) 186 of the outer sheath 180, as shown inFIGS. 16B and 17B. The expandable sheath 120 may then be expanded to itsenlarged condition, as shown in FIGS. 16C and 17C. The separatedportions 188 of the outer sheath 180 may be substantially flexible suchthat they do not interfere substantially with the expansion of theexpandable sheath 120 and/or may conform substantially to the shape ofthe expandable sheath 120 as it expands.

In a further alternative, with reference to FIGS. 1A-2B, when aconstraint is provided around the sheath 20, the sheath 20 need not beattached to the stiffening member 12. The sheath 20, e.g., a tubularbody, may simply be disposed around the stiffening member 12 and folded,twisted, crimped, wrapped, or otherwise compressed into the contractedcondition around or adjacent to the stiffening member 12 before beinginserted into or otherwise constrained by the constraint. In addition oralternatively, vacuum pressure, either alone or in conjunction withfolding, may be used to compress the sheath 20 and/or fluid may beinfused into the lumen 26 to expand the sheath 20, as explained furtherbelow.

Although only one stiffening member 12 is shown in FIGS. 1A-2B, it willbe appreciated that a sheath apparatus in accordance with the presentinvention may include more than one stiffening member. For example, asshown in FIGS. 9A and 9B, an embodiment of a sheath apparatus 210 isshown that includes two stiffening members 212 to which an expandablemembrane or other sheath 220 is attached. The sheath 220 may becompressed to a contracted condition, shown in FIG. 9A, e.g., bytwisting the stiffening members 212 about longitudinal axis 218 to windthe sheath 220 around the stiffening members 212. The sheath 220 may beunwound and expanded to an enlarged condition, shown in FIG. 9B, byuntwisting the stiffening members 212, thereby providing lumen 226within the sheath 220.

In addition, although the stiffening members 12, 212 shown in FIGS.1A-2B, 9A, and 9B extend generally parallel to the longitudinal axis 18,218, other stiffening members may also be provided in addition orinstead of the stiffening member(s) 12, 212. For example, as shown inFIGS. 10A and 10B, one or more reinforcing members 312 may be providedthat extend helically around a tubular sheath 320. The reinforcingmembers 312 may be wires or other strands attached to an outer or innersurface of the sheath 320 or embedded within a wall of the sheath 320.One or more helical reinforcing members may also facilitate expandingand/or collapsing the sheath 320. For example, ends of the reinforcingmember(s) 312 may pulled axially away from one to compress the sheath320. In addition or alternatively, the reinforcing member(s) 312 may bebiased to expand, e.g., towards the configuration shown in FIG. 10B, tofacilitate expanding the sheath 320 towards the enlarged condition.

In addition or alternatively, one or circumferential or peripheral ringsor strands (not shown) may be provided around the sheath 320. Suchreinforcing rings or strands may support the sheath 320 and/or bias thesheath 320 towards the enlarged condition, similar to the helicalreinforcing member(s) described above.

Further, although the apparatus described above include an expandablesheath having a single lumen, it will be appreciated that it may bepossible to provide one or more sheaths, each including one or morelumens therein. For example, a sheath may be fabricated to have multiplelumens, e.g. by extrusion. As a further example, a plurality ofexpandable sheaths, similar to those described above, may be attached toone another and/or to one or more common stiffening members to providean apparatus with multiple expandable lumens (not shown). The sheathsmay be concentric with one another, e.g., disposed loosely within oneanother, or attached along one or more edges to one another.Alternatively, the sheaths may be disposed adjacent to one another,e.g., attached together or to one or more common stiffening members.Thus, multiple instruments may be advanced through respective lumens ofthe sheaths in conjunction with one another.

Optionally, one or more of the components of the sheath apparatusdescribed above, e.g., stiffening member(s), sheath, and/or constraint,may include one or more radiopaque markers, e.g., bands or otherelements made from radiopaque material, radiopaque inks or otherdepositions, and the like (not shown). Such markers and/or radiopaquematerial may facilitate imaging and/or monitoring the apparatus duringits use, e.g., using fluoroscopy. In addition, markers may be providedthat are spaced relative to one another in a predetermined manner, e.g.,at known distances from one another, to denote distances and/orfacilitate mapping and/or accessing a patient's vasculature.Alternatively, other external or internal imaging systems and methodsmay be used, e.g., magnetic resonance imaging (“MRI”), ultrasound, andthe like, as is well known in the art.

A sheath apparatus in accordance with the present invention may be usedto provide access to a variety of body lumens, e.g., to perform adiagnostic and/or therapeutic procedure. Generally, the apparatus, withan expandable sheath in a contracted condition, may be introduced intoan entry site, e.g., a natural or created opening in a patient's body,and advanced into one or more body passages, including created passages,e.g., dissection planes, within the patient's body. Preferably, theapparatus is advanced from the entry site until a distal end of thesheath is disposed within a target body lumen while a proximal end ofthe sheath remains outside the entry site. Because of its low profile,the apparatus may be easily advanced through tortuous anatomy until thedistal end is disposed within relatively small, difficult to access bodylumens.

The sheath may then be expanded to an enlarged condition, therebydefining a lumen within the sheath. Thus, the lumen defined by thesheath may extend from the entry site through any intervening bodypassages to the target body lumen or site to provide a path from theentry site to the target body lumen or site. Optionally, if, asdescribed above, the sheath is maintained and/or covered in thecontracted condition by a constraint, the constraint may be at leastpartially removed from the sheath before the sheath is expanded to theenlarged condition.

A diagnostic and/or therapeutic procedure, such as the exemplaryprocedures described below, may be performed within the body lumen viathe lumen defined by the sheath. Upon completing the procedure(s), thesheath may be withdrawn from the body lumen, and preferably from thepatient's body.

For example, as shown in FIGS. 11A-11F, a sheath apparatus 10 may beused to facilitate delivering a stent 60 within a stenosis or occlusion92 within a blood vessel 90. The vessel 90 may be an artery or veinwithin a coronary, carotid, cerebral, or other vessel, e.g., within apatient's coronary, peripheral, or neuro vasculature.

As shown in FIG. 11A, the apparatus 10, with the sheath 20 in itscontracted condition, may be advanced from a percutaneous entry site(not shown) and introduced into the patient's vasculature, until thedistal end 16 is disposed within the target vessel 90. For example, aguidewire (not shown) may be previously placed from the percutaneousentry site to the vessel 90 beyond the stenosis 92 using conventionalmethods. The apparatus 10 may be advanced over the guidewire until thedistal end 24 of the sheath 20 is positioned within or beyond thestenosis 92, as shown in FIG. 11A. If the apparatus 10 includes astiffening member 12, the stiffening member 12 may include a guidewirelumen (not shown) such that the guidewire may be inserted through theguidewire lumen to advance the apparatus 10 over the guidewire.Alternatively, the sheath 20, in its contracted condition may beadvanced without a previously placed guidewire. The distal tip of thesheath 20 or stiffening member 12 may facilitate navigation through thevasculature, e.g., by being substantially flexible or floppy, to avoidtrauma to the vasculature during advancement, or by being shaped,shapeable, or deformable to enable steering during advancement.

Once the apparatus 10 is positioned within the vessel 90, any constraint(not shown) maintaining the sheath 20 in the contracted condition orotherwise covering the sheath 20 may be removed, e.g., mechanically,chemically (e.g., bio-absorbable sutures), and/or physiologically (e.g.,heat-activated nitinol ties). For example, as described above, this mayinvolve retracting an overlying catheter or sheath (not shown), orremoving loops or other strands (also not shown) surrounding the sheath20.

The sheath 20 may then be expanded from its contracted condition to itsenlarged condition. For example, a fluid (not shown) may be introducedinto the lumen 26 to expand the sheath 20, e.g., such that the sheath 20expands to line or otherwise contact walls of one or more vessels withinthe patient's vasculature, e.g., between the entry site and the vessel90. Alternatively, the sheath 20 may simply be released such that thesheath 20 is free to expand as one or more instruments, such as thecatheter 62 and stent 60, are advanced through the lumen 26, as shown inFIG. 11B.

With continued reference to FIG. 11B, one or more instruments may beintroduced through the lumen 26 defined by the sheath 20 into the vessel90. For example, a catheter 62 carrying the stent 60 may be introducedinto the proximal end 22 (not shown in FIGS. 1A-11F) of the sheath 20and advanced through the lumen 26 until the stent 60 is located withinthe vessel 90. The stent 60 may be any known endoprosthesis, e.g., aballoon-expandable or self-expanding stent, and the catheter 62 mayinclude any known delivery apparatus, e.g., including a balloon, sheath,nose cone, and/or other elements. Optionally, other instruments, e.g.,thrombectomy devices, agitation devices, balloon catheters, filters,occlusion devices, and the like (not shown) may be introduced throughthe sheath 20 before or after the catheter 62, e.g., to dilate thestenosis 92 and/or to provide distal protection, i.e., capture embolicmaterial released during the procedure.

The guidewire or other rail over which the apparatus 10 may be advancedmay be removed before any instrument(s) are advanced through the sheath20, or the guidewire may remain in place across the stenosis 92. Inaddition, if the apparatus 10 includes a concentric stiffening member 12within the sheath 20, the catheter 62 may be advanced over thestiffening member 12, i.e., between the stiffening member 12 and thesheath 20 as shown in FIG. 11B. Alternatively, the stiffening member 12may be removed from the sheath 20 if the sheath is detachable from thestiffening member 12 (not shown). In a further alternative, such as thatshown in FIGS. 4A and 4B, the instrument(s) (not shown in FIGS. 4A and4B) may be advanced through the lumen 126 adjacent to the stiffeningmember 12. Thus, one advantage of delivering a catheter or otherinstrument within the sheath 20 is that there may be no need for aguidewire lumen in the instrument, which may allow the profile of theinstrument to be reduced as compared to instruments that are deliveredover a guidewire.

With continued reference to FIG. 11B, the lubricious nature of thesheath 20 may facilitate advancing the catheter 62 through the lumen 26,and, consequently, through any narrow, tortuous, diseased, and/orfriable regions of the patient's vasculature. For example, the sheath 20may translate axial forces, e.g., created when an instrument, such asthe catheter 62, is pushed against or into a narrow region, into radialforces that may facilitate dilating the narrow region to accommodate theinstrument passing therethrough. This action may be enhanced further bypressurizing the sheath 20 internally, e.g., by introducing a fluid intothe lumen 26. Thus, the sheath 20 may facilitate advancing the stent 60across the stenosis 92, as shown in FIG. 11C.

In addition, the sheath 20 may substantially reduce the risk ofperforating or otherwise damaging the walls of vessels within thevasculature and/or snagging an instrument, since the sheath 20 may guideany instruments advanced through the sheath 20 along the lubricious pathof the lumen 26. Further, the sheath 20 may minimize the risk of embolicmaterial and the like from being dislodged from the patient'svasculature, since the sheath 20 may expand to line the walls, therebyrestraining plaque, thrombus, and the like between the sheath 20 and thevessels' walls.

If the distal end 24 of the sheath 20 is closed, an opening 28 may becreated to accommodate advancing one or more instruments through thelumen 26 and out of the sheath 20. For example, as explained above, thedistal end 24 may be separated from the stiffening member 12 when thefirst instrument, e.g., the catheter 62 carrying the stent 60 isadvanced through the lumen 26 and against the distal end 24, as shown inFIG. 11D. Alternatively, if the distal end 24 of the sheath 20 isattached to a stiffening member 12, the distal end 24 may be separatedfrom the stiffening member 12, e.g., by advancing the stiffening member12 distally and/or retracting the sheath 20 proximally, to create theopening 28, e.g., before or after introducing the catheter 62 or otherinstrument (not shown) into the lumen 26.

In a further alternative, as shown in FIG. 5 and described above, thesheath 20′ may include a weakened region 30′ in the distal end 24′ thatmay be used to create an opening (not shown in FIG. 5). For example, afluid, e.g., saline and/or contrast, may be introduced into the lumen26′ of the sheath 20′ until sufficient internal pressure is created tocause the weakened region 30′ to rupture or tear. Alternatively, aninstrument (e.g., the catheter 62 shown in FIGS. 11B-11F, a guidewire,and the like, not shown), may be advanced into the lumen 26′ and pushedagainst the weakened region 30′ to cause the weakened region 30′ to failand create an opening. In still a further alternative, an apparatus 10,″such as that shown in FIG. 6, may be used that includes a sheath 20″with an opening 28″ already provided in the distal end 24.″

Turning to FIG. 11E, once the stent 60 is positioned across the stenosis92, the sheath 20 may be at least partially retracted to expose thestent 60 and/or the catheter 62 within the vessel 90 and/or stenosis 92.The stent 60 may be expanded, as shown in FIG. 11F, e.g., usingconventional methods to dilate and/or scaffold the stenosis 92. Once thestent 60 is delivered (and any additional procedures completed), thecatheter 62 and the apparatus 10 may be removed from the vessel 90, andthe patient's vasculature via the entry site.

In one embodiment, the catheter 62 or other instruments (not shown) mayfirst be removed into and through the sheath 20, whereupon the sheath 20may be removed. If desired, the sheath 20 may be collapsed at leastpartially from the enlarged condition before removing the sheath 20 fromthe vessel 90 by aspirating any fluid from within the lumen 26 of thesheath 20, e.g., by connecting a source of vacuum to the proximal end 22of the sheath 20. Alternatively, a catheter or other tubular member (notshown) may be advanced over the sheath 20 to facilitate its removal. Inanother alternative, the sheath 20 may be removed simultaneously withthe catheter 62 or other instrument(s), e.g., by retracting theinstrument(s) into the sheath 20. In yet another alternative, the sheath20 may be removed from the patient before the catheter 62 or otherinstrument(s) are removed. It will be appreciated that external imaging,e.g., fluoroscopy, MRI, and/or ultrasound, may be used to monitor theprocedure, and that any of the components, e.g., the apparatus 10, thestent 60, and/or the catheter 62 may include elements, e.g., radiopaquemarkers (not shown) for facilitating such imaging during theiradvancement and/or removal.

Turning to FIGS. 12A-12D, another method is shown that uses a sheathapparatus 10 (or any of the sheath apparatus described above) forproviding access to a target vessel within a patient's vasculature.Specifically, the apparatus 10 may be used to deliver an electrical lead70, e.g., for a pacemaker, into a coronary vein 96, e.g., adjacent tothe left ventricle of the heart. As shown in FIG. 12A, initially, theapparatus 10 may be advanced into the coronary vein 96 with anexpandable sheath 20 carried by a stiffening member (not shown) in itscontracted condition.

For example, with the sheath 20 collapsed, the apparatus 10 may beintroduced from a percutaneous entry site (not shown), e.g., a femoralvein or subclavian vein, and advanced through the patient's venoussystem into the right atrium of the heart, and into the coronary sinus(not shown) to reach the target coronary vein 96. The apparatus 10 maybe advanced over a guidewire (not shown), similar to the previousmethods. Because of its relatively low profile, the apparatus 10 may beable to access smaller coronary veins or be advanced further into atarget coronary vein than conventional devices.

Once the apparatus 10 is positioned within or near a target vein 96,fluoroscopy and/or other external imaging may be used to facilitatepositioning the apparatus 10. The apparatus 10, e.g., the distal end 24of the sheath 20, an overlying constraint, and the like (not shown), mayinclude one or more radiopaque markers (not shown) to facilitate suchimaging. In addition or alternatively, contrast may be introduced intothe vein, e.g., via a fluid lumen in a stiffening member (not shown) ofthe apparatus 10 and/or through the lumen 26 of the sheath 20, tofacilitate fluoroscopic imaging. Such imaging may be used to identifythe location of the sheath 20 relative to nearby structures, e.g., toensure that the apparatus 10 is advanced as close as possible to atarget location. Preferably, the apparatus 10 is advanced such that thedistal end 24 of the sheath 20 is disposed within a coronary vein 96adjacent the left ventricle of the patient's heart (not shown).

As shown in FIG. 12B, the sheath 20 may be expanded between the entrysite and the target vein 96. If a constraint (not shown) is provided, itmay be removed before expanding the sheath 20. A fluid, e.g., includingsaline and/or contrast, may be introduced into the sheath 20 to expandthe sheath 20 towards its enlarged condition. Contrast delivered intothe sheath 20 may also facilitate imaging the vein 96. For example, ifthe distal end 24 of the sheath 20 is initially closed, contrastdelivered into the lumen 26 may cause the sheath 20 to expand andconform to the shape of the surrounding vessels, thereby facilitatingimaging of the vessels through which the sheath 20 is deployed.

As shown in FIGS. 12B and 12C, an electrical pacing lead 70 may beadvanced through the lumen 26 of the sheath 20 until a tip 72 of thelead 70 is disposed within the target vein 96. Similar to the methodsdescribed above, the sheath 20 may already include an opening 28 in itsdistal end 24 that communicates with the lumen 26 or an opening may becreated in a closed sheath distal end 24 (not shown). The tip 72 may bedeployed from the sheath 20, e.g., by retracting the sheath 20 oradvancing the tip 72 through the opening 28 beyond the distal end 24 ofthe sheath 20, thereby substantially anchoring the tip 72 within thevein 96.

As shown in FIG. 12D, the sheath 20 may then be removed from the vein 96and from the patient's vasculature. Preferably, the sheath 20 may besplit into one, two, or more pieces to allow the sheath 20 to be removedeasily from around the lead 70. Implantation of the lead 70 may then becompleted using conventional methods.

Turning to FIGS. 14A-14C, another method is shown for delivering acolonoscope 76 into a patient's colon 98 using a sheath apparatus 10,such as any of the embodiments described above. As shown in FIG. 14A,the apparatus 10 is advanced into the colon 98 with the sheath 20 in itscontracted condition. Once advanced to a desired location, the sheath 20may be expanded to an enlarged condition to define a lumen 26, as shownin FIG. 14B. The colonoscope 76 may be advanced through the lumen 26 ofthe sheath 20, similar to the previous embodiments. If desired, thesheath 20 may be configured such that the colonoscope 76 may imagesurrounding tissue within the colon 76 as the colonoscope 76 is advancedthrough the sheath 20. For example, the material of the sheath 20 may besubstantially transparent to visible light (or other portions of thespectrum) that is used by the colonoscope 76. Alternatively, in otherapplications, the sheath 20 may allow other imaging sources, e.g.,ultrasound energy, to pass substantially freely through the sheath 20 toallow imaging of the surrounding tissue. The sheath 20 may be removedfrom around the colonoscope 76, as shown in FIG. 14C, or may remain atleast partially around the colonoscope 76, e.g., to facilitate itsremoval after a procedure. In addition, the sheath 20 may be adapted forintroducing fluid, e.g., air, carbon dioxide and the like, into thegastrointestinal lumen.

Turning to FIGS. 15A-15D, a sheath apparatus in accordance with thepresent invention may facilitate advancement of one or more instrumentsretrograde into a patient's venous system. For example, as shown in FIG.15A, an exemplary vein 102 is shown that includes a plurality of valves104. A sheath apparatus 10 (which may be any of the embodimentsdescribed herein) may be advanced into the vein 102 with an expandablesheath 20 in its contracted condition, as shown in FIG. 15B. Onceadvanced to a desired position, the sheath 20 may be expanded to itsenlarged condition, as shown in FIG. 15C, thereby opening the valves 104and provided a relatively large bore lumen 26 through the vein 102. Oneor more instruments, such as the stent 60 and catheter 60 shown in FIG.14D, may be advanced through the lumen 26 to complete a procedure,similar to the embodiments described above.

A sheath apparatus according to the present invention may also be usedto perform other diagnostic and/or therapeutic procedures within thevasculature. For example, the apparatus may provide an expandable lumenfor delivering an imaging element, e.g., an intravascular ultrasound(“IVUS”) device, endoscope, fiber optic element, and the like, and/orfor delivering therapeutic instruments, e.g., angioplasty catheters,stent delivery devices, atherectomy or thrombectomy devices, and thelike.

In alternative methods, a sheath apparatus in accordance with thepresent invention may be used to provide access and/or deliverinstruments to other body lumens within a patient's body. For example,the apparatus may be used within a patient's urogenital tract,respiratory tract, gastrointestinal tract, lymphatic system, or vascularsystem. In addition, the apparatus may be introduced into surgicallycreated openings and advanced into surgically created passageways, e.g.,a passageway created within interstitial space, e.g. to obtain a biopsy.

Turning to FIGS. 18 and 19A-19C, another embodiment of a sheathapparatus 510 is shown, in accordance with the present invention.Generally, the apparatus 510 includes a catheter or other elongatemember 512 and an expandable sheath 520. The catheter 512 may be anelongate tubular body formed from uniform or variable flexibilitymaterial, e.g., having a substantially flexible distal end 514. Thecatheter 512 may include one or more lumens (not shown) extending fromits proximal end (also not shown) to the distal end 514.

In a preferred embodiment, the catheter 512 includes one or morediagnostic or therapeutic elements 516 on the distal end 514. Forexample, the catheter 512 may include an imaging element, such as anintravascular ultrasound (“IVUS”) device, and the like, and/or adissection element, such as a cutting element, an element for bluntdissection, or an ablation element, e.g., for observing, crossing,and/or treating an occlusion within a blood vessel (not shown). Inaddition or alternatively, the catheter 512 may include a steeringelement (also not shown) for manipulating the distal end 514 within apatient's body.

The sheath 520 may be a substantially flexible, and preferably flimsy,membrane or other structure. For example, the sheath 520 may include anyof the materials and/or structures included in any of the embodimentsdescribed previously. The sheath 520 may be substantially permanentlyattached to an outer surface 518 of the catheter 512. For example, thesheath 520 may include a sheet whose longitudinal edges are attached atone or more locations along a length of the catheter 512. Alternatively,the sheath 520 may be a tubular member having an outer surface that isattached at one or more locations along the length of the catheter 512.Thus, the sheath 520 may extend at least partially between the proximalend and the distal end 514 of the catheter 512.

The sheath 520 may be expandable from a contracted condition (shown inFIG. 19A), e.g., to minimize a profile of the sheath 520, and anenlarged condition (shown in FIGS. 19B and 19C). In the enlargedcondition, the sheath 520 may at least partially define an accessorylumen 522. The accessory lumen 522 may extend between a proximal end(not shown) and a distal end 524 of the sheath 520, preferablyterminating adjacent the distal end 514 of the catheter 512.

The distal end 524 of the sheath 520 may include an opening (not shown)communicating with the accessory lumen 522. Alternatively, the distalend 524 may be closed, and may include a break-away portion for creatingan opening (not shown) such that an instrument (such as a guidewire 580,shown in FIG. 19C) inserted through the lumen 522 may be advanced fromthe opening into a body lumen, similar to the previous embodiments.

Optionally, a constraint (not shown) may be provided for maintaining thesheath 520 in the contracted condition, e.g., as the apparatus 510 isadvanced through a patient's body. For example, an outer sheath (notshown) may be provided for receiving the catheter 512 and the sheath520) that may be removed before the sheath 520 is expanded. In additionor alternatively, an adhesive may be used to temporarily secure thesheath 520 along the outer surface 518 of the catheter 512. Thus, theadhesive may retain the sheath 520 substantially flat along the outersurface 518 of the catheter 512, as shown in FIG. 19A. The adhesive mayrelease when internal pressure is delivered into the lumen 522 of thesheath 520 or may dissolve within a body lumen to release the sheath 520to allow the sheath 520 to expand.

Turning to FIGS. 20A-20D, a method is shown for delivering aninstrument, e.g., a guidewire 580 through a total occlusion 592, e.g.,within a blood vessel or other body lumen 590, e.g., using the apparatus510 shown in FIG. 18. Initially, as shown in FIG. 20A, with the sheath520 in its contracted condition, the apparatus 510 may be introducedinto the vessel 590, e.g., via a percutaneous entry site (not shown),until the distal end 514 of the catheter 512 is located proximally(e.g., upstream) relative to the occlusion 592.

Turning to FIG. 20B, the distal end 514 of the catheter 512 maybeadvanced through the occlusion 592 until the distal end 524 of thesheath 520 is disposed distally (e.g., downstream) relative to theocclusion 592. The catheter 512 may include one or more elements 516 onthe distal end 514 for facilitating advancing the catheter 512 throughthe occlusion 592. For example, the catheter 512 may carry an imagingelement, e.g., an IVUS device (not shown), on the distal end 514 forimaging the occlusion. In addition or alternatively, a dissectionelement, e.g., a cutting, core, blunt dissection, and/or ablationelement (not shown), may be provided on the distal end 514 for creatinga passage 594 through the occlusion. Optionally, the catheter 512 mayinclude a steering element (not shown) to facilitate manipulating thedistal end 514 of the catheter 512 as it is advanced through theocclusion 592.

Once the sheath 520 extends through the occlusion 592, an elongatemember, e.g., a guidewire 580 or other instrument (not shown), may beinserted through the sheath 520 until a distal end 582 of the guidewire580 is disposed distal to the occlusion 592. The sheath 520 may beexpanded as the guidewire 580 or other instrument is advanced throughthe sheath 520. Alternatively, the sheath 520 may be dilated, e.g., byintroducing a fluid into the lumen 522 (see FIG. 29B) of the sheath 520,similar to the embodiments described above.

The apparatus 510 may then be withdrawn through the occlusion 592 and/orout of the vessel 590. One or more instruments (not shown) may then beadvanced over the guidewire 592, e.g., to treat the occlusion 592 and/orto deliver agents or fluids distally beyond the occlusion 592, as iswell known to those skilled in the art. Thus, unlike the previousembodiments, the sheath 520 may provide a lumen for a secondary device,e.g., a guidewire, that may be delivered in cooperation with thecatheter 512.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the appended claims.

What is claimed is:
 1. An apparatus for providing access to a body lumenof a patient, comprising: a flexible stiffening member having a proximalend and a distal end having a size and shape for insertion into a bodylumen and defining a maximum outer cross-section, the stiffening memberbeing flexible to facilitate advancement through tortuous anatomy; andan expandable sheath extending from the proximal end to the distal endof the stiffening member and attached to the stiffening member distalend, the sheath being expandable from a contracted condition to minimizea profile of the sheath to allow insertion along with the stiffeningmember into a body lumen, and an enlarged condition wherein the sheathat least partially defines a lumen extending between the proximal anddistal ends of the stiffening member, the lumen having an inner diameterlarger than the maximum outer cross-section of the distal end of thestiffening member.
 2. The apparatus of claim 1, wherein the stiffeningmember comprises a distal tip that extends beyond the distal end of thesheath.
 3. The apparatus of claim 1, wherein the stiffening membercomprises a substantially atraumatic distal tip.
 4. The apparatus ofclaim 1, wherein the stiffening member is received in a separate pocketor lumen of the sheath that extends between proximal and distal ends ofthe sheath.
 5. The apparatus of claim 4, wherein the stiffening memberis attached to the sheath within the lumen.
 6. The apparatus of claim 1,wherein the sheath comprises a lubricious material.
 7. The apparatus ofclaim 1, wherein the stiffening member comprises an elongate memberextending substantially parallel to a longitudinal axis of the sheath.8. The apparatus of claim 1, wherein the sheath is attached to thestiffening member at one or more locations.
 9. The apparatus of claim 8,wherein the sheath is attached to the stiffening member at the proximaland distal ends of the stiffening member.
 10. The apparatus of claim 8,wherein the sheath is attached substantially continuously to thestiffening member between the proximal and distal ends of the stiffeningmember.
 11. The apparatus of claim 1, wherein the stiffening membercomprises a guidewire lumen extending between the proximal and distalends, the guidewire lumen having an inner diameter smaller than theinner diameter of the lumen of the expandable sheath in the enlargedcondition.
 12. The apparatus of claim 1, further comprising a “J” tip onthe distal end of the stiffening member.
 13. The apparatus of claim 1,wherein the stiffening member has a maximum outer cross-section betweenabout 0.05-5 millimeters.
 14. The apparatus of claim 1, wherein thestiffening member has a maximum outer cross-section between about 0.2-2millimeters.
 15. The apparatus of claim 1, further comprising a handleon the proximal end of the sheath and wherein the sheath extends fromthe handle to the stiffening member distal end.
 16. An apparatus forproviding access to a body lumen of a patient, comprising: a flexiblestiffening member having a proximal end, a distal end having a size andshape for insertion into a body lumen and defining a maximum outercross-section, the stiffening member being flexible to facilitateadvancement through tortuous anatomy and having sufficient length to beadvanced from a location outside a patient's body through anyintervening body passages into a site to be accessed; and an expandablesheath expandable from a contracted condition to minimize a profile ofthe sheath and an enlarged condition, the expandable sheath being flimsyand extending between the proximal and distal ends of the stiffeningmember, the sheath being expandable from the contracted condition toallow insertion along with the stiffening member into a body lumen, andthe enlarged condition wherein the sheath at least partially defines alumen extending between the proximal and distal ends of the stiffeningmember, the lumen of the sheath having an inner diameter larger than themaximum outer cross-section of the distal end of the stiffening memberin the enlarged condition.
 17. The apparatus of claim 16, wherein thesheath may be split into one or more pieces to allow the sheath to beremoved easily from around an electrical lead advanced through the lumenof the sheath.
 18. The apparatus of claim 16, further comprising anelectrical lead that may be advanced through the lumen of the sheathafter the sheath has been advanced along with the stiffening member tothe site to be accessed.
 19. The apparatus of claim 16, wherein thestiffening member is received in a separate pocket or lumen of thesheath that extends between proximal and distal ends of the sheath. 20.The apparatus of claim 16, wherein the stiffening member extendssubstantially parallel to a longitudinal axis of the sheath.
 21. Theapparatus of claim 16, wherein the sheath is attached to the stiffeningmember at one or more locations.
 22. The apparatus of claim 16, thestiffening member further comprising one or more lumens extendingbetween the proximal and distal ends.
 23. The apparatus of claim 16,wherein the apparatus has a low profile defining an outer diameter orother maximum cross-section when the expandable sheath is in thecontracted condition, and wherein the inner diameter of the lumen isbetween about three and ten times larger than the diameter or othermaximum cross-section of the low profile of the apparatus.
 24. Theapparatus of claim 16, wherein the apparatus defines an outer diameteror other maximum cross-section between about 0.1 and about tenmillimeters (0.1-10 mm) when the expandable sheath is in the contractedcondition, and wherein the inner diameter of the lumen of the expandablesheath is larger than the outer diameter or other maximum cross-sectionof the apparatus when expanded to the enlarged condition.
 25. Anapparatus for providing access to a body lumen of a patient, comprising:a flexible stiffening member having a proximal end, a distal end havinga size and shape for insertion into a body lumen, and one or more lumensextending between the proximal and distal ends; and an expandable sheathextending from the proximal end to the distal end of the stiffeningmember, the sheath being expandable from a contracted condition tominimize a profile of the sheath to allow insertion along with thestiffening member into a body lumen, and an enlarged condition whereinthe sheath at least partially defines a lumen extending between theproximal and distal ends of the stiffening member, the sheath comprisinga lubricious coating for facilitating inserting one or more instrumentsthrough the lumen, wherein the apparatus has an outer profile when theexpandable sheath is in the contracted condition between about 0.1 andabout ten millimeters (0.1-10 mm), and wherein the expandable sheathdefines a lumen in the enlarged condition that is larger than the outerprofile and having a diameter or other maximum cross-section betweenabout 0.3 and about one hundred millimeters (0.3-100 mm).
 26. A systemfor treating a patient via a body lumen, comprising: a flexiblestiffening member having a proximal end, and a distal end having a sizeand shape for insertion into a body lumen and defining an outerdiameter; an expandable sheath extending between the proximal and distalends of the stiffening member, the sheath being expandable from acontracted condition to minimize a profile of the sheath to allowinsertion along with the stiffening member into a body lumen, and anenlarged condition wherein the sheath at least partially defines a lumenextending between the proximal and distal ends of the stiffening member,the lumen of the sheath having an inner diameter in the enlargedcondition larger than the outer diameter of the distal end of thestiffening member; and an electrical lead advanceable through the lumenof the sheath after the sheath has been advanced along with thestiffening member into a desired body lumen of a patient, wherein thesheath comprises a lubricious coating for facilitating inserting thelead through the lumen.
 27. An apparatus for providing access to a bodylumen of a patient, comprising: an expandable flimsy, inelastic sheathcomprising a proximal end, a distal end, and a length sufficient for thesheath to extend between an entry site into a patient's body and atarget body lumen, the sheath being expandable from a contractedcondition to minimize a profile of the sheath to allow insertion into abody lumen, and an enlarged condition wherein the sheath at leastpartially defines a lumen extending between the proximal and distalends; and one or more flexible reinforcing members extending along thesheath, the one or more reinforcing members having a cross-sectionsmaller than the lumen of the sheath in the enlarged condition, whereinthe apparatus has an outer profile when the expandable sheath is in thecontracted condition defining a first diameter or other maximumcross-section, and wherein the expandable sheath defines a lumen havinga second inner diameter or other maximum cross-section in the enlargedcondition that is between about three and ten times larger than thefirst diameter or other maximum cross-section of the outer profile ofthe apparatus.